Makes 8 servings
3 lbs (6 bunches) fresh spinach
1-1/4 cups 2% or 3% milk
1 cup whipping (35%) cream
1 leek, finely chopped, white and light green parts only
1/4 cup butter
1/4 cup all-purpose flour
Generous pinch freshly grated nutmeg
½ cup grated Parmesan cheese (optional)
Cook spinach in batches in boiling, salted water until wilted, 1 to 2 minutes. Drain in a colander and let cool. Squeeze small handfuls of spinach to remove as much moisture as possible, then coarsely chop.
Heat milk and cream in a small saucepan over moderate heat, stirring, until warm. Meanwhile, cook leek in butter in a 3-quart heavy saucepan over medium-low heat, stirring occasionally, until softened, about 5 minutes. Whisk in flour and cook roux, whisking, 3 minutes. Add warm milk mixture in a fast stream, whisking constantly to prevent lumps, and simmer, whisking, until thickened, 3 to 4 minutes. Stir in nutmeg, spinach, Parmesan cheese and salt and pepper to taste and cook, stirring, until heated through.
*This dish can be made ahead. Transfer to casserole dish and reheat in 350°F oven for about 20 minutes or until heated through.